In the prior art, when an IV bag is injected into the patients, even if the IV fluid is injected completely into the patients, there were cases that the protectors or the patients could not recognize the state, and thus the blood of the patients flows reversely. Therefore, there was a problem that the patients or the protectors should always watch the injection state with very keen attention even during the injection of the IV fluid because they could not know exactly the time when the injection of the IV fluid is completed.
Accordingly, an invention was developed in which a small round ball is inserted into a drip chamber of an IV set, and if the IV fluid is injected completely, the round ball blocks the outlet of the IV set, and thus prevents the patients' blood from flowing reversely.
But, such a conventional invention could not solve the problem that when the IV fluid is injected completely, the round ball can not block the outlet of the IV set surely, and thus the patients or the protectors are not satisfied.